Early signs of cardiovascular compromise often go unnoticed in older women, partly because they are manifest by different symptoms than the classic ones in men such as chest pain. Thus preventing heart disease in postmenopausal women is important. Cardiovascular Disease (CVD) and stroke are associated with systemic inflammation, the cause of which is partially unknown. In this proposed study we will identify processes in the gut mucosa that cause or are associated with systemic inflammation in HIV+ women who are being treated with ART. The menopausal transition in women is characterized by declining endothelial function and increasing systemic inflammation and increased risk of CVD. These processes are directly or associated with the changes in sex hormones levels, mainly estradiol (E2) and testosterone (T). Intestinal barrier function is essential to prevent potentially harmful microbes in the lumen from gaining access to the underlying lamina propria. Lack of estradiol (E2) affects gut barrier function and the penetration of gut microbes through the epithelial barrier, thus affecting an immune response mounted by the gut to prevent the spread of these organisms. An increased level of T-cell activation and decreased levels of E2 have been observed in peripheral blood of healthy HIV- post-menopausal compared to pre-menopausal women which is likely to allow for increased microbial translocation in the gut. We hypothesize that decreased tight junction (TJ) formation and a decline of intestinal epithelial barrier integrity in post-menopausal HIV+ women is induced by the loss/decline of E2 and/or Estrogen receptor (ER) levels and is associated with increased plasma CVD risk indicators. We propose that the compromised gut epithelium in post-menopausal HIV+ women may contribute to local and systemic T cell activation due to microbial translocation and increase their risk of developing CVD. Specific Aim 1 will investigate the in-vivo relationship of serum E2 and gut ER? levels with TJ formation, immune activation, composition of bacterial translocation in the gastrointestinal mucosa, and CVD risk. In Specific Aim 2 we will elucidate in-vitro mechanisms (ER engagement and alternate pathways) of the effect of E2 on epithelial growth, TJ formation and vascular endothelium in the presence and absence of HIV. The major innovation includes that for the first time, the role of gut epithelial integrity will be studied with regard to its contribution to CV risk in postmenopausal HIV+ women, using a unique sample of biopsies from the gut. This unique set of samples from healthy pre- and postmenopausal HIV+ and HIV- women, and use of innovative methodologies of visualization of protein-protein interaction and the tensile strengths associated with that interaction will provide invaluable scientific evidence o understand and promote future studies aimed at improving mucosal and cardiovascular health in HIV+ women.